(a) Field of the Invention
The present invention relates to a photovoltaic device and a manufacturing method thereof.
(b) Description of the Related Art
A solar cell is one kind of photovoltaic device for converting light energy into electrical energy, and is used as a core element for developing solar light. The solar cell is a diode consisting of a PN junction, and may be classified into various kinds according to the material used as a light absorption layer.
A solar cell using silicon as the light absorption layer may be classified as a crystalline (monocrystalline and polycrystalline) solar cell, a substrate solar cell, and a thin film (crystalline and amorphous) solar cell. Also, a representative solar cell may be a compound thin film solar cell using CIGS (CuInGaSe2) or CdTe, a III-V group solar cell, a dye response solar cell, and an organic solar cell.
The thin film solar cell is formed by coating a film onto a substrate based on thin glass or plastic. With the common thin film solar cell, the diffusion distance of carriers is very short due to the characteristic of the thin film compared to that of the crystalline silicon solar cells, and if it is fabricated only with the PN junction structure, the collection efficiency of electron-hole pairs generated by the sunlight is significantly lowered. Therefore, the thin film solar cell has a PIN structure where an intrinsic semiconductor-based light absorbing layer with high light absorption is interposed between the P-type and N-type semiconductors. The common thin film solar cell has a structure where a front transparent conductive film, a PIN layer, and a rear reflective electrode layer are sequentially deposited on a substrate. In this structure, the light absorbing layer is depleted due to the overlying P and underlying N layers with a high doping concentration so that an electric field is generated therein. As a result, among the carriers generated in the light absorbing layer by sunlight, the electrons are collected at the N layer and the holes at the P layer by way of drift of the internal electric field, thereby generating an electric current.
However, when the PIN layer is formed in the vertical direction, several laser patternings are executed to the cells when connecting the electrodes of the P layer and the N layer of different cells such that layer damage may be generated and a remaining layer is generated on the side, thereby generating pattern deterioration. Accordingly the efficiency of the solar cell may be reduced.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.